/* Ppmd.h -- PPMD codec common code
   2010-03-12 : Igor Pavlov : Public domain
   This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */

#ifndef __PPMD_H
#define __PPMD_H

#include "Types.h"
#include "CpuArch.h"

EXTERN_C_BEGIN

#ifdef MY_CPU_32BIT
    #define PPMD_32BIT
#endif

#define PPMD_INT_BITS 7
#define PPMD_PERIOD_BITS 7
#define PPMD_BIN_SCALE (1 << (PPMD_INT_BITS + PPMD_PERIOD_BITS))

#define PPMD_GET_MEAN_SPEC(summ, shift, round) (((summ) + (1 << ((shift) - (round)))) >> (shift))
#define PPMD_GET_MEAN(summ) PPMD_GET_MEAN_SPEC((summ), PPMD_PERIOD_BITS, 2)
#define PPMD_UPDATE_PROB_0(prob) ((prob) + (1 << PPMD_INT_BITS) - PPMD_GET_MEAN(prob))
#define PPMD_UPDATE_PROB_1(prob) ((prob) - PPMD_GET_MEAN(prob))

#define PPMD_N1 4
#define PPMD_N2 4
#define PPMD_N3 4
#define PPMD_N4 ((128 + 3 - 1 * PPMD_N1 - 2 * PPMD_N2 - 3 * PPMD_N3) / 4)
#define PPMD_NUM_INDEXES (PPMD_N1 + PPMD_N2 + PPMD_N3 + PPMD_N4)

/* SEE-contexts for PPM-contexts with masked symbols */
typedef struct
{
    UInt16 Summ; /* Freq */
    Byte Shift; /* Speed of Freq change; low Shift is for fast change */
    Byte Count; /* Count to next change of Shift */
} CPpmd_See;

#define Ppmd_See_Update(p)  if ((p)->Shift < PPMD_PERIOD_BITS && --(p)->Count == 0) \
    { (p)->Summ <<= 1; (p)->Count = (Byte)(3 << (p)->Shift++); }

typedef struct
{
    Byte Symbol;
    Byte Freq;
    UInt16 SuccessorLow;
    UInt16 SuccessorHigh;
} CPpmd_State;

typedef
#ifdef PPMD_32BIT
CPpmd_State*
#else
UInt32
#endif
CPpmd_State_Ref;

typedef
#ifdef PPMD_32BIT
void*
#else
UInt32
#endif
CPpmd_Void_Ref;

typedef
#ifdef PPMD_32BIT
Byte*
#else
UInt32
#endif
CPpmd_Byte_Ref;

#define PPMD_SetAllBitsIn256Bytes(p) \
    { unsigned i; for (i = 0; i < 256 / sizeof(p[0]); i += 8) { \
          p[i + 7] = p[i + 6] = p[i + 5] = p[i + 4] = p[i + 3] = p[i + 2] = p[i + 1] = p[i + 0] = ~(size_t)0; } }

EXTERN_C_END

#endif